1. Field of the Invention
The present application relates to an encapsulation film and a method of encapsulating an organic electronic device (OED) using the same.
2. Discussion of Art
An OED is a device including an organic material layer generating exchange of charges using holes and electrons, and may be, for example, a photovoltaic device, a rectifier, a transmitter, and an organic light emitting diode (OLED).
An OLED among the OEDs consumes less power and has a higher response speed than conventional light sources, and is preferable as a thin display device or light. In addition, the OLED has excellent space utilization, and thus is expected to be applied in various fields including all kinds of portable devices, monitors, notebook computers, and TVs.
To expand compatibility and use of the OLED, the most important problem is durability. Organic materials and metal electrodes included in the OLED are very easily oxidized by external factors such as moisture, and a product including the OLED is very sensitive to environmental factors. Recently, as a panel becomes larger and a bezel becomes shorter, thereby decreasing a distance between an external atmosphere and an organic diode, when the OLED is encapsulated using the same material as the previously used material, device reliability due to moisture permeation is reduced. When a content of a moisture adsorbing agent to compensate for a shorter bezel is increased, an absolute value of expansion by a reaction with moisture becomes higher, and thus failure of adhesion or damage to lower layers may occur. Accordingly, various methods have been suggested to effectively prevent permeation of oxygen or moisture into the OED such as an OLED.
Conventionally, a method of processing a metal can or glass in the form a cap having a groove and loading a powder-type desiccant absorbing moisture in the groove, or processing a metal can or glass in a film type and adhering it using a double-sided tape.
In Japanese Patent Laid-Open Publication No. Hei 9-148066, an organic EL diode including a stacked structure having a structure in which an organic emitting layer formed of an organic compound is disposed between a pair of electrodes facing each other, an airtight container blocking such a stacked structure from an external atmosphere, an alkali metal oxide contained in the airtight container, and a drying means such as the alkali metal oxide is disclosed. However, such an organic EL diode is increased in a total thickness of the display device due to the shape of the airtight container, is vulnerable to a physical impact due to an internal space, and has a poor dissipating characteristic when manufactured in a large scale.
In U.S. Pat. No. 6,226,890, a method of drying an electric diode employing a moisture absorbing layer formed using a moisture adsorbent including a solid particle having a particle size of 0.1 to 200 μm and a binder is disclosed, but the method does not provide sufficient moisture adsorbability. When a water vapor transmission rate (WVTR) in a cured state does not meet 50 g/m2·day or less due to the characteristic of the binder surrounding the moisture adsorbent, a moisture adsorption speed is high during an acceleration test, and thus the diode cannot exhibit sufficient performance.
To improve this, according to Korean Unexamined Patent Application No. 2007-0072400, a speed of permeating moisture into an OLED may be reduced by adding a moisture adsorbent to an epoxy sealant to chemically adsorb moisture in the OLED, but expansion of a volume caused by a reaction between the moisture adsorbent and moisture can make physical damage to the OLED. In addition, when a metal oxide is used as a moisture adsorbent, it may react with moisture, thereby producing a strong base material to chemically damage a protective layer and a negative electrode layer.
Therefore, there are demands for developing encapsulants which can ensure long-term reliability, effectively prevent permeation of moisture, and reduce damages to the OED.